The present invention relates generally to gypsum compositions, and more specifically to lightweight, foamed gypsum compositions and products made therefrom.
Gypsum boards have been commonly employed in construction, such as interior walls, ceilings, and acoustical tiles and panels. It is well known that gypsum boards, particularly in ceiling applications, tend to sag or fail under high humidity conditions. When in contact with water, the water absorbed by the gypsum dry walls may dissolve the gypsum and reduce the mechanical strength of the material. This can be particularly problematic where the washability of the panels is desired.
Dispersions of epoxy reins with hardening agents have been used to improve the strength of coating materials. U.S. Pat. No. 5,475,039 discloses hardening agents for aqueous epoxy resins. U.S. Pat. No. 6,274,650 discloses the making of liquid epoxy encapsulants comprising a basic bisphenol-type epoxy resin with epoxy groups and an amine hardening agent. U.S. Pat. No. 4,966,927 discloses an in-situ reaction to generate a hardening agent from the mixing of methylene chloride and monoethanol amine. The new hardening agent can be mixed with epoxy and have a long pot life. The new binder can be used to improve overlay coatings for concrete or asphalt surface.
Incorporations of epoxy resins/hardeners in concrete and cement are known in the prior art. For example, JP 11,139,858A discloses a mixture of epoxy resins, polyamine and wet concrete or mortar to protect concrete from an acid rain to prolong a service life. U.S. Pat. No. 5,162,060 discloses the use of hydraulic cement, ureido-functional latex, epoxy hardening agent, and epoxy to improve cement chemical resistance. JP 63,310,757A discloses the making of a workable concrete having high strength and low shrinkage by using epoxy resin and a hardening agent (a mixture of polycondensate of xylenediamine, phenol and formalin, and polyamide). JP11,028,717A discloses a preparation by blending epoxy resin either in cement, sand, or other aggregates with a hardening agent in an aqueous mixture. JP 08,208,295A discloses the use of epoxy (glycerol diglycidyl ether) and water-reducing agent for concrete with an epoxy resin hardener (ethylenediamine) to provide fluidity and to give good mechanical strength. JP 07,257,952A discloses the formulation of hydraulic cement with bisphenol A and epichlorhydrine type epoxy resins to obtain a high strength polymer concrete. JP 03,069,538A discloses the acceleration of hardening of cement and the prevention of shrinkage and cracking due to drying by blending cement with epoxy resin, Portland cement, calcium aluminate, gypsum, epoxy resin hardening agent, and set regulating agent, and water. It was stated that the formation of calcium hydroxide or xe2x80x98slaked limexe2x80x99 in the cement hydration process and the resulting alkaline by-products hydrolyzed the epoxy resins and adversely reduced the epoxy efficiency.
Incorporation of epoxy resins in the production of lightweight concrete is also known in the prior art. For example, JP 02,006,378A discloses the production of lightweight cellular concrete by mixing cement, aggregate, water, and an epoxy resin (bisphenol A/epichlorohydrin type epoxy resin emulsion) to shorten demolding time. A 3-10% by weight of epoxy resin based on 100 parts of cement was also disclosed in the patent. A foam agent was introduced into the cement slurry to make a lightweight cellular concrete.
JP 4,292,445A discloses the blending of cement with a lightweight fine aggregate, epoxy resins, and polyester resin to provide a cement composition having sufficient strength.
U.S. Pat. No. 5,696,174, owned by Allied Foam Tech, discloses foamed gypsum for making boards, panels, roof decking, and flooring.
U.S. Pat. No. 4,403,006 discloses the incorporation of coal fly ash in a gypsum slurry used in forming lightweight gypsum boards and a method of producing those boards.
It is an object of the present invention to provide a composition of high performance foamed gypsum boards. Another objective is to provide a non-cementitious hydraulic mix where epoxy will have prolonged life without the alkalinity from hydrolyzed cement. It is another objective to provide lightweight foamed gypsum boards with foam stability not adversely affected by the addition of epoxy and amines. The improved lightweight foam gypsum boards can be used in the building construction for interior walls, ceilings, and acoustical tiles and panels that give high compressive strength, high bending strength, good surface abrasive resistance, washability, and excellent sagging resistance.
The present invention is a lightweight, foamed gypsum composition that has high compressive strength and also high bending strength. The improved lightweight foam gypsum boards made in accordance with the present invention provide good surface abrasion resistance, wash resistance, and sagging resistance. The improved lightweight foam gypsum boards can be used in building construction for interior walls, ceilings, and acoustical tiles and panels, among other uses. The foamed gypsum composition of the present invention comprises gypsum, a foaming agent, epoxy resin, and a hardener.
Epoxies and hardeners tend to induce significant foam collapse when conventional surfactants or protein-based foam agents are used. No prior art is known to produce lightweight gypsum foam materials with a combination of epoxy resins and hardener agents. In accordance with the present invention, foaming agents, such as those disclosed in U.S. Pat. No. 5,696,174, are used to make stable preformed foams for lightweight and foamed gypsum materials. The addition of epoxy resins and hardeners do not adversely affect the foam stability of the improved lightweight and foamed gypsum compositions in the present invention. The improved lightweight gypsum boards with the addition of epoxy resins and hardeners demonstrate high compressive strength, high bending strength, good surface abrasion resistance, washability, and excellent sagging resistance. This makes the improved lightweight and foamed gypsum boards particularly useful as interior walls, ceilings, and acoustical tiles and panels.
More specifically, the present invention uses epoxy resins and hardeners in conjunction with the improved lightweight and foamed gypsum materials, and the foam stability of the lightweight and foamed gypsum compositions is not adversely affected by the addition of epoxy resins and hardeners. In accordance with the present invention, gypsum slurries are prepared by mixing gypsum and water. The gypsum slurries are further blended with epoxy resins and hardeners. The gypsum foams in the present invention are prepared by adding the preformed foams into the resulting gypsum slurries under agitation until the wet density of the foam slurries reach 5 to 100 pounds per cubic foot (pcf). A preferred embodiment may optionally contain 0.1-15 parts epoxy resins, and 0-15 parts hardening agent, per 100 parts gypsum.
The foaming agents with excellent foam stability and water resistance in the present invention are prepared by a preformed foam composition formed of a long-chain organic cation-forming compound having the general formula (I): 
where R is an aliphatic hydrocarbon radical having from 8 to 24 carbon atoms; R1 is selected form the group consisting of an alkyl group having from 1-16 carbon atoms, a hydroxyalkyl group having from 1-16 carbon atoms, a benzyl group, a group which, when taken together with the nitrogen, represents a heterocyclic radical, and any of such groups having a hydrogen atom replaced by a fluorine atom; R2 and R3 are selected form the group consisting of an alkyl group having form 1-6 carbon atoms, a hydroxyalkyl group having from 1-6 carbon atoms, a benzyl group, a hydrogen atom, a group which, when taken together with the nitrogen, represents a heterocyclic radical, and any of such groups having a hydrogen atom replaced by a fluorine atom; and Xxe2x88x92 is an anionic counter ion; and a long-chain anionic forming compound having the formula (II): 
where Rxe2x80x2 is an aliphatic hydrocarbon radical with 10 to 24 carbon atoms; X2xe2x88x92 is an anionic group selected from the group consisting of carboxylate, sulfate, sulfonate, and phosphate; and Y+ is a cationic counter ion selected from the group consisting of ammonium, sodium, and potassium salt; wherein the long-chain organic cation formed from (I) and the long-chain organic anion formed from (II) are present in a weight ratio of from 0.05:1 to 15:1. The gypsum foam slurries made with the above preferred foaming agents give excellent foam stability. The detailed preparation of the foams is found in U.S. Pat. No. 5,696,174.
The epoxy resins in this invention are commonly formed by reacting epichlorohydrin with desired polyepoxides, such as glycidyl ether of 2,2xe2x80x2-bis(4-hydroxyphenyl)propane, n-butyl gylcidyl ether of 2,2xe2x80x2-bis(4-hydroxyphenyl)propane, glycidyl ethers of 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, polyglycidyl ether of 1,1,5,5-tetrakis(hydroxyphenyl)pentane, and (chloromethyl)oxirane 4,4xe2x80x2-(1-methylethylidene)bisphenol. Other epoxy resins suitable for use in the present invention include bisphenol F epoxy resins, such as bisphenol F epoxy resin and epoxy phenol Novolac; di(2,3-epoxybutyl)phthalate; di(2,3-epoxybutyl)adipate; di(2,3-epoxy octyl)terephthalate; 2,3-epoxybutyl 3,4-epoxypentanoate; 3,4-epoxypropyl 3,4-epoxyhexanoate; a synthetic polymer latex having ureido functional groups described in U.S. Pat. No. 5,162,060 and references therein; or a mixture of two or more epoxy resins.
The hardening agents in this invention comprise anhydrides, such as phthalic anhydride; alkylamine, such as a fatty amine; polyether diamine such as Jeffamine ED 900 (Jefferson Chemical Co., Inc., Houston, Tex.), polyakylene polyamines, such as, such as diethylene triamine, triethylene tetramine, tetraethylene pentamine, N,Nxe2x80x2-bis-(2-aminopropyl)-ethylene diamine, and m-phenylenediamine; cylcoaliphatic diamines, such as 3-aminomethyl-3,5,5-trimethyl clclohexylamine, and m-xylene diamine.
The additional additives of this invention include inert fillers, aggregates, clay, sand, fibers, pigments, dyes, polymeric cement binder, plasticizers, superplasticizers, mineral wool, scrim, freeze-preventative additives, and combinations of these additives.
The addition of epoxy resins and hardeners do not adversely affect the foam stability of lightweight foam gypsum compositions in the present invention. The improved lightweight foam gypsum boards with the addition of epoxy resins and hardeners give high compressive strength, high bending strength, good surface abrasive resistance, washability, and excellent sagging resistance. This makes the improved lightweight foam gypsum boards useful as boards, interior wall panels, ceiling tiles, acoustical tiles, acoustical panels, roof decking, and flooring.